PLC 5 Processor Faulted when PID enabled. Need Help

I just programmed a PID control system for a VFD to control header pressure for our weak liquor pump to our evaporators. I tested out all the motor control logic as well as tested the adjustment registers for the the set point and output logic with the Delta-V HMI. At this point I did not have the PID enabled because I was not ready for it. As soon as I enabled "B3:1/0" which enables the rung to the PID the Processor Faulted and it damn near took the Evaporators down. I attached the program so you guys could have a look and see what mistake I have obviously made. Please help as I'm expected to commission this system tomorrow afternoon.

Thanks, Tex

** edit, I noticed that the process variable for the PID I used is also used at the PV for another PID and I also had forgot to set the Update time for the PID. I don't know if this helps but I thought I'd try.

I forgot to mention the PID address is PD80:24

I don't have software available right now to look at your program, but you almost certainly have an out of range number in one of your PID parameters.

I think I got it figured out. I had the timer in rung120 set for 1 second to update the PID Loop time. But in the PID I had a value of 0 entered for loop update time. I have a test rack and processor in my office and downloaded this program onto it and when I enabled the PID it faulted and I got a chance to look at the fault and it said I had "entered a negative time value in a PID instruction". Once I cleared the fault and put in the update time as "1" I put the processor back into Run mode and no issues. I feel like an idiot definite learning lesson!!

sparkytex said:

I think I got it figured out. I had the timer in rung120 set for 1 second to update the PID Loop time. But in the PID I had a value of 0 entered for loop update time. I have a test rack and processor in my office and downloaded this program onto it and when I enabled the PID it faulted and I got a chance to look at the fault and it said I had "entered a negative time value in a PID instruction". Once I cleared the fault and put in the update time as "1" I put the processor back into Run mode and no issues. I feel like an idiot definite learning lesson!!

Click to expand...

It got me once. After that, I was very careful to check all of my parameters before enabling a PID instruction. An SLC will do the same thing.